Epigenetic-mediated upregulation of progesterone receptor B gene in endometrial cancer cell lines.

Objectives: To determine if epigenetic interference can restore progesterone receptor-B (PR-B) expression in PR-B negative endometrial adenocarcinoma cell lines, and to characterize the kinetics of PR-B induction mediated by DNA methyltransferase and histone deacetylase inhibitors.

Methods: The PR-B negative endometrioid cancer cell lines KLE and HEC-1B were used as study models. PR-B mRNA and protein expression levels were measured using real-time PCR and Western blot analysis, respectively. DNA methylation levels of the PR-B promoter were determined by methylation-specific PCR. Dose-response correlations and the duration of response to aza-deoxycytidine (ADC) and trichostatin A (TSA) were characterized. Cell responses to prolonged and repeated drug treatment were also examined.

Results: Relatively low concentrations of ADC and TSA over a 24-h period induced PR-B expression. Furthermore, ADC and TSA acted synergistically to reactivate PR-B expression. Depending on the cell line used, PR-B mRNA was induced 10-110 fold. This elevated PR-B expression continued for 48 h after drug withdrawal. Sustained upregulation of PR-B mRNA and protein was observed during prolonged and repeated drug treatment.

Conclusion: The epigenetically silenced PR-B gene remains sensitive to changes in DNA demethylation and histone acetylation in uterine adenocarcinoma cell lines. Treatment with ADC and/or TSA results in a robust and sustainable PR-B upregulation. These small molecule epigenetic modifying agents may be used to sensitize poorly differentiated, PR-B negative endometrial cancers to progestational therapy.